Remote Sensing-Driven Analysis of Hourly Urban Heat Storage and Its Effects on Air Temperature in China

Urban heat storage (Qs) is a critical contributor to the urban heat island (UHI) effect, yet its spatiotemporal patterns and quantitative contribution remain poorly understood. Urban surface thermal properties directly influence Qs, but accurately quantifying these properties at a regional scale remains a challenge. This study retrieves urban thermal inertia (TI) and hourly Qs based on heat conduction theory, using 24-hour cycles of Himawari-8 land surface temperature (LST), in three urban agglomerations of China. The quantitative impact of Qson near-surface air temperature (Ta) is also investigated at both city and local climate zones (LCZs) scales. With validation of Qsagainst flux tower data, the correlation coefficient can be up to 0.92 and RMSE is 39 W/m2. Results show that there is a significantly stronger correlation of Qswith Taduring nighttime (R2>0.95) than daytime, confirming its dominant control in nocturnal UHI. To be specific, across local climate zones (LCZ), high-rise and open-built areas exhibited greater nocturnal Qs(and correspondingly higher Ta) compared to compact mid-low-rise neighborhoods. Notably, water bodies remain higher Qs(higher Ta) than vegetated surfaces. Entropy-based thermodynamic assessment suggests high-rise buildings exhibit higher but faster UHI change than low-rise. For future urban planning, we recommend prioritizing the heat mitigation of high-rise buildings and strategically planning blue space to balance its daytime cooling against nocturnal warming effects.